This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Our goal is to determine if, and to what extent, dietary supplementation with quercetin affects the heat shock protein response following 7 days of heat acclimation. We believe that athletes and others who use antioxidants in combination with work in hot environments may be blocking specific adaptations that provide protection during repeated heat stress. We hypothesize that supplementing subjects with quercetin while they exercise to achieve heat acclimation will significantly suppress HSP72 levels, which may negate HSP72 ability to reduce intestinal permeability following heat acclimation. This investigator initiated study will involve a repeated-measures design (2 conditions) in which subjects will perform exercise in the heat. Each condition will begin with an Intestinal Permeability Measurement (IP1), where subjects will be admitted to the General Clinical Research Center (GCRC), drinking a test solution and collecting their urine for 8 hours to measure intestinal integrity prior to heat stress. This will be followed by a Heat Tolerance Trial (HT1), used as a baseline measurement of subject's capacity to work in the heat. Following HT1 each subject will perform 7 Days of Heat Acclimation (HA). On days 1 and 7 of HA subjects will follow exercise by performing additional Intestinal Permeability Measurements, providing pre (IP2) and post acclimation (IP3) measurements of intestinal permeability. Day 6 of HA will provide a posttest measurement of subjects'capacity to work in the heat, and will be synonymous with Heat Tolerance Trial 2 (HT2).